sandbox: rng: Add a random number generator(rng) driver

Add a sandbox driver for random number generation. Mostly aimed at
providing a unit test for rng uclass.

Signed-off-by: Sughosh Ganu <sughosh.ganu@linaro.org>
Reviewed-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

1 files changed, 56 insertions, 0 deletions

diff --git a/drivers/rng/sandbox_rng.c b/drivers/rng/sandbox_rng.c
new file mode 100644
index 0000000000..cd0b0ac77b
--- /dev/null
+++ b/drivers/rng/sandbox_rng.c
@@ -0,0 +1,56 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2019, Linaro Limited
+ */
+
+#include <common.h>
+#include <dm.h>
+#include <rng.h>
+
+#include <linux/string.h>
+
+static int sandbox_rng_read(struct udevice *dev, void *data, size_t len)
+{
+	unsigned int i, seed, random;
+	unsigned char *buf = data;
+	size_t nrem, nloops;
+
+	if (!len)
+		return 0;
+
+	nloops = len / sizeof(random);
+	seed = get_timer(0) ^ rand();
+	srand(seed);
+
+	for (i = 0, nrem = len; i < nloops; i++) {
+		random = rand();
+		memcpy(buf, &random, sizeof(random));
+		buf += sizeof(random);
+		nrem -= sizeof(random);
+	}
+
+	if (nrem) {
+		random = rand();
+		memcpy(buf, &random, nrem);
+	}
+
+	return 0;
+}
+
+static const struct dm_rng_ops sandbox_rng_ops = {
+	.read = sandbox_rng_read,
+};
+
+static const struct udevice_id sandbox_rng_match[] = {
+	{
+		.compatible = "sandbox,sandbox-rng",
+	},
+	{},
+};
+
+U_BOOT_DRIVER(sandbox_rng) = {
+	.name = "sandbox-rng",
+	.id = UCLASS_RNG,
+	.of_match = sandbox_rng_match,
+	.ops = &sandbox_rng_ops,
+};